1. Field of the Invention
The present invention relates to paper machines, and, more particularly, to a guide for moving a paper roll in a paper machine and thereby steering a moving fiber web.
2. Description of the Related Art
Paper machines typically include a belt which is used to carry a fiber material disposed across the width thereof, such as a fiber web in the form of a paper web. The belt is carried by a plurality of rolls, and may be in the form of, e.g., a polyester forming fabric, felt, conveyor belt, or dryer fabric. A plurality of belts may be provided which successively carry the fiber web from one end of the paper machine to the other end. Such belts can generally be viewed as conveying, dewatering and drying belts.
To properly position the belt on the paper machine during operation, it is necessary that the belt be "steered" such that the belt moves a predetermined amount from side to side on the machine during operation. Typically, a mechanical paddle disposed on each side of the belt may be engaged by the belt upon occurrence of sideways movement of the belt past a predetermined threshold. Actuation of the paddle in turn causes a roll guide to move an end of a selected paper roll in a predetermined transverse direction relative to the longitudinal axis of the selected roll. Such transverse movement of the roll causes the belt to move back toward the opposite side of the machine, thus maintaining the belt in proper running alignment on the paper machine.
Conventional roll guides used for moving a roll in a transverse direction relative to the longitudinal axis of the roll typically include a roll mounting frame to which an end of the roll is connected. The roll mounting frame is connected to a further support frame using a pair of rigid arms which are pivotally attached at opposing ends thereof to the roll mounting frame and support frame using a reduced friction bearing assembly, such as a spherical roller bearing. The rigid arms oscillate over a very limited range of movement as the roll mounting frame is moved in the transverse direction by a positioning device, such as a hydraulic ram, screw or the like. In other words, the pair of rigid arms, roll mounting frame and further support frame essentially define a 4-bar linkage with the roll mounting frame and further support frame being disposed generally parallel to each other and the pair of rigid arms being disposed generally parallel to each other. Application of a transverse force by the hydraulic ram, screw, etc., moves the roll mounting frame from side to side, while still maintaining the roll mounting frame generally parallel to the further support frame.
A problem with conventional paper roll guides is that the anti-friction bearings at respective ends of the pair of rigid arms associated with each roll guide undergo only limited oscillatory movement. The anti-friction bearings include metallic bearing elements and such limited oscillatory movement does not allow proper elastro-hydrodynamic lubrication of the metallic bearing elements, such as by formation of an oil film between the inner and outer races, and allows metal to metal contact to occur in the bearing. When such metal to metal contact occurs, "brinelling" results. Brinelling and subsequent spalling result in permanent deformation of the bearing and shortened life of the paper roll guide.
What is needed in the art is a paper roll guide which is simpler and less expensive than conventional paper roll guides, and which avoids the problem of proper lubrication of bearings present in conventional paper roll guides.